Investigations of the neuroeffector mechanism in vascular tissue will focus on a number of specific objectives: the definition of the basis of variation and characteristics of blood vessels of different size and location; the quantitation of the vascular neurogenic response mediated through beta adrenergic receptors; the development of the neuroeffector mechanism in umbilical, placental and fetal vascular tissue; the response of the vascular neuroeffector to a rapid rise in intravascular pressure and the basis of regulation of the neuroeffector relationship. BIBLIOGRAPHIC REFERENCES: Bevan, R.D., E. Van Marthens and J.A. Bevan: "Hyperplasia of vascular smooth muscle in experimental hypertension in the rabbit." Circ. Res. Supp. II, 38:58-62, 1976. Bevan, J.A., R.D. Bevan, P.C. Chang, B.L. Pegram, R.E. Purdy and C. Su: "Changes in the contractile response of arteries and veins from hypertensive rabbits to sympathetic nerve activity: Assessment of some postsynaptic influences." Blood Vessels 13:167-180, 1976.